Understanding the fundamental aspects of the spatial associations, development, and birth defects of the muscles and skeleton in non-pentadactyl limbs

ABDALA, V; KHOLSDORF, T.; DIOGO, R.

Washington DC

Congreso; International Congress of Vertebrate Morphology; 2016

The International Society of Vertebrate Morphology (ISVM)

Tetrapod limbs are claimed to be major features that fostered radiation of vertebrates across different environments, from which the habitat transition from water to land is one of the most spectacular ever seen. There is an impressive morphological variation in both forelimbs and hindlimbs of tetrapods: for instance, they may shape like a bird wing or a whale fin, or may be rudimentary or even completely absent. However, this remarkable morphological variability does not imply a change in the type of tissues that compose a limb, which, in wildtype animals, always has skin, nerves, blood vessels, cartilages, bones, muscles and tendons associated in a fine, functional way.In particular, limb muscles and bones are usually superimposed, in a sharp spatial association between homologous skeletal elements and the muscular groups attached to them. However, comparative, experimental and medical studies on the developmental interactions between these structures remain limited, and mainly refers to cases of pentadactyly. Data obtained from non-pentadactyl limbs are crucial to clarify how the functional and spatial associations between limb bones and muscles change during evolution and in human birth defects, and therefore to understand both the evolution of several major vertebrate groups that include non-pentadactyl animals (e.g., birds, crocodylians, frogs, urodeles) and the implications and applications for medicine. Notably, non-pentadactyly is among the most common limb defects in humans, and is one of the major causes for limb surgery, particularly in babies and children.In this symposium we present an overview on the new insights that have been recently produced in the field of limb research, with special attention to non-pendatadactyl limbs and to hard tissue and soft tissue interactions, including data from studies on human birth defects, experimental developmental studies of mice and chicken, mathematical modeling (e.g. suggesting that digits may form via a Turing model), genetic studies, and work on fossils. We aim to contribute to the understanding of both the patterns and processes in limb evolution, and pave the way for broader discussions within the fields of comparative, developmental and evolutionary biology.